Assessing environmental and radiological impacts and lithological mapping of beryl-bearing rocks in Egypt using high-resolution sentinel-2 remote sensing images

Emerald and other beryls represent a family of the most valuable gemstone around the world and particularly in Egypt. Beryllium (Be) contents in beryl-bearing bedrocks in south Sinai (Wadi Ghazala and Wadi Sedri), and in central and south Eastern Desert of Egypt (Igla area, Zabara-Um Addebaa belt, Homret Akarem, and Homret Mukpid) were investigated in this study. The environmental risk levels of Be, associated major ions, and heavy metals in groundwater nearby to beryl-bearing mineralization were also evaluated. Results showed that Be contents ranged from 1 to 374 ppm in beryl-bearing bedrocks, while in nearby groundwater, Be content has a range of 0.0001–0.00044 mg/L with an average of 0.00032 mg/L, which is within the permissible levels and below (0.004) the U.S. EPA maximum contaminant level (MCL). Most levels of heavy metals (e.g., Be, B, Ni, V, Fe, and Al) in the investigated groundwater of central and south Eastern Desert and south Sinai are within the permissible levels and below their corresponding U.S. EPA MCLs. This study also investigated the radiological risk of natural radionuclides distributed in beryl-bearing bedrocks in the study area using gamma spectrometry; Sodium Iodide [NaI(Tl)] scintillation detector. Among the estimated mean 238U, 232Th, and 226Ra activity concentrations of the studied beryl-bearing rocks, Homret Mukpid (79, 87.15, 60.26 Bq kg−1) and Homret Akarem (111.6, 51.17, 85.1 Bq kg−1) contain the highest values. This may be attributed to their highly fractionated granitic rocks that host uranium and thorium reservoir minerals such as zircon, allanite, and monazite. The estimated data of multi-radiological parameters such as absorbed gamma dose, outdoor and indoor annual effective dose, radium equivalent activity, internal and external indices, index of excess cancer, and effective dose to human organs reflecting no significant impacts from the emitted natural gamma radiation.

. The cloud-free Sentinel-2A images were automatically atmospherically corrected and orthorectified using the Sentinel Application Platform (SNAP) software as summarized in Fig. 6. These approaches used histogram treatments, image enhancement, and subset tools, and all Sentinel-2A VNIR bands were re-sampled to (10 × 10 m) pixel size (Fig. 6). Band ratios were applied for better lithological discrimination 25 (Fig. 6). A false-color (RGB) composite contains a large volume of information, including topographic information and geological roughness. Therefore, Principal Component Rock sampling and analysis of Be concentrations. Representative rock samples (1 kg/sample) were collected from six beryl-bearing bedrock occurrences in south Sinai, CED, and SED of Egypt ( Fig. 1), to determine the Be concentrations in the studied bedrocks. The analysis of the geochemical samples was carried out using Ultra-Trace Inductively Coupled Plasma Mass Spectrometer (ICP-MS) at Bureau Veritas Labs, Canada. A 0.25 g split was heated in an acid mixture (HNO 3 , HClO 4 , and HF) to fuming and drying, while the residue was dissolved in HCl.
Groundwater sampling and analysis of Be and associated heavy metals. To assess the groundwater quality parameters, the environmental risk of Be, associated heavy metals and their potential impacts on the environment and human health, a total of ten groundwater samples were collected from the main five shallow and productive groundwater wells: W. Ghazala (depth to water: 5 m; Fig. 7a) and W. Sedri (depth to water: 13 m; Fig. 7b) in South Sinai, and Igla (depth to water: 0 m; Fig. 7c   Statistical analysis. Univariate (min, max and mean) and bivariate were applied to the investigated concentrations of Be and heavy metals in beryl-bearing rocks and nearby groundwater in this study using Statgraphics software 41 .
Radiological risk assessment indices. The concentration of uranium (ppm), thorium (ppm), radium (ppm) and potassium (%) of the examined six areas of emerald and beryl-bearing rocks at W. Ghazala (7 samples), W. Sedri (7 samples) in south Sinai, Igla (6 samples; CED), Zabara-Um Addebaa belt (10 samples), Homret Akarem (3 samples), and Homret Mukpid (7 samples), SED of Egypt, were measured using Sodium Iodide [NaI(Tl)] scintillation detector' with a 76 × 76 mm at Nuclear Material Authority. It is characterized by low cost, flexibility in shape, size, and linear energy. The best resolution is observed at 6% when measuring the 662 keV gamma ray from 137Cs. A cylindrical Pb shield detector with fixed bottom and cover was used to reduce γ-ray background. Pb shield includes an inner Cu cylinder (0.3 mm thick) to absorb the generated X-rays in the lead shield. Background distributions were determined using the empty specification package. The grinded samples (300-400 g) from the studied rocks were put in plastic containers, sealed well, and left for at least 21 days to accumulate free radon. The activity of 226 Ra was estimated based on γ-lines with energies 351.9 keV (36.7%) of 214 Pb and the 609.3 keV (46.1%), 1120.3 keV (15%), and 1764 keV (15.9%) of 214Bi. In the case of 232Th, 911.2 keV (29%), γ-lines of 228Ac and 238.6 keV (43.6%) γ-peak of 212 Pb have been used. 40 K activity was estimated using the 1461 keV (10.7%) γ-peak. Therefore, NaI detectors are suitable. Radiological risk parameters were estimated in the prospecting emerald and beryl-bearing rocks from six areas to infer the radiation effect on human organs. These parameters include absorbed gamma dose, outdoor and indoor annual effective dose, radium equivalent activity, internal and external indices, index of excess cancer, and effective dose to human organs.
Absorbed gamma-dose rate (D air ). This index is used to evaluate the released gamma rays more than one meter from the Earth's surface 40,42-45 . 226 Ra, 232 Th, and 40 K activity concentrations are used to estimate the D air as follows: where Ra, Th and K are 226 Ra, 232 Th, and 40 K activity concentrations, respectively.
Radium equivalent activity (Ra eq ). Ra eq is attributed to external and internal alpha particles and gamma-ray exposure dose. 226 Ra, 232 Th, and 40 K activity limits are used to estimate the proper Ra eq index in the examined six areas as follows 16  (2) Ra eq Bq kg −1 = Ra + 1.43 Th + 0.077 K

Results and discussion
Lithological mapping of beryl-bearing bedrocks using remote sensing data. The Proterozoic basement rocks including beryl-bearing occurrences in south Sinai appear on the composite of Red-Green-Blue (RGB) image in Sentinel-2A false color (8, 4, 2, Fig. 8a) in dark to light red color. The sedimentary rocks (e.g., limestone) appear in rose-pink, and the Quaternary alluvial cover appears in beige to grey color, particularly in the northern and southwestern sides of the image (Fig. 8a).
Specifically, in W. Sedri, southwestern Sinai area, the Sentinel-2A PCA composite (4, 3, 2) image showed two major lithological rock units with distinctive boundaries, orthogneiss (OG), which is crossed-cut by berylbearing quartz veins and appears in light green to the right side, and pink granite (PG) which easily recognized by dark brownish red color in the left side of the image (Fig. 8b). In W. Ghazala, southeastern Sinai, the Sentinel-2A PCA composite (4, 3, 2) image showed three rock units, besides pink granite (PG), gneissose granite (GG), which associated with beryl mineralization, appears in orange-brown rust color, while small patches of metagabbrometadiorite (MG) appears in a sharp blue color the left-downside of the image (Fig. 8c). The more altered soils and wadi deposits are dissected by the drainage network and show a blue-green color (Fig. 8b,c).
The Proterozoic basement rocks hosting beryl mineralization in CED, and SED of Egypt appear on the composite RGB image in Sentinel-2A false color (8, 4, 2, Fig. 9) with comparable lithological rock units and corresponding colors to south Sinai (Fig. 8a). In Igla mine area, CED, where mines of tin and other metals were common, but without any beryl occurrences, the Sentinel-2A PCA composite (4, 3, 2) image showed three rock units; pink granite (PG) with dark brownish red color, metagabbro-metadiorite (MG) appears in a light blue in the middle part of the image, and patches of metasediments (MS) with a very dark blue color near the leftdownside of the image (Fig. 10a).
In Zabara-Um Addebaa belt, SED, the Sentinel-2A PCA composite (4, 3, 2) image indicated six rock units with distinctive boundaries; pink granite (PG) with dark brownish red color, ophiolitic metagabbro (OMG) appears in dark green color, metasediments (MS), where phlogopite schist contains beryl mineralization, appears in light greenish blue color, undifferentiated metamorphic rocks (MT) with a purple color, and few patches of gneissose granite (GG) with a dark blue color, and gneiss (GN) with a dark brown color (Fig. 10b). In Homret Akarem and Homret Mukpid areas, SED, the Sentinel-2A PCA composite (4, 3, 2) image indicated three rock units with distinctive boundaries; pink granite (PG) appears with brownish to pinkish red color, where beryl mineralization occurs within pegmatite veins, metasediments (MS) with light green color, and metavolcanics (MV) with dark green color (Fig. 10c). The more altered soils and wadi deposits in CED, and SED are dissected by the drainage network and show a blue-green color (Fig. 10a-c).

Environmental risk assessment of Be concentrations in beryl-bearing bedrocks and nearby groundwater. Beryllium concentration in beryl-bearing bedrocks.
A total of thirty-four representative rock samples, which collected from beryl-bearing bedrock occurrences in South Sinai (W. Ghazala and W. Sedri) and (3) AED out mSv y −1 = D air nGy h −1 × 8.76 h/y × 0.2 × 0.7 Sv Gy −1 × 10 −3 www.nature.com/scientificreports/ has two paragenetic types: emerald in mica-schists and beryl in granitoids 6,12 . Be occurrence depends strongly on geology, thus Be is concentrated in mafic minerals and muscovite (10-50 ppm) and in plagioclase up to 20 ppm 23 . Additionally, the highest naturally occurring concentrations of Be are found in certain pegmatite bodies 53 . Abdalla 44 reported Be concentrations with a range of 0.001-0.007% in beryl-bearing granitoids (Homret Akarem, Homret Mukpid, and Qash Amir) in the Eastern Desert of Egypt. Abdel Gawad et al. 45 investigated the geochemistry and genesis of beryl crystals (up to 10 mm in size) from the ancient Roman mines at Wadi Nugrus, SED, Egypt. They reported that the emerald of Wadi Nugrus occurs along the contact zone between biotite schists, pegmatites, and quartz veins, and has similarities with the geological setting of the Canadian This study investigated Be concentrations in beryl-bearing bedrock occurrences in South Sinai, CED, and SED of Egypt. Findings showed that Be concentrations ranged from 1 to 4 ppm with an average of 1.5 ppm in orthogneiss rocks at W. Sedri, southwest Sinai, to 10-374 ppm and an average of 76 ppm in granitic rocks at W. Ghazala, southeast Sinai (Table 2). Be was not detected in the bedrocks of the Igla area, CED, while in SED, Be has a range of 8-49 ppm and an average of 19.6 ppm in phlogopite schist rocks along Zabara-Um Addebaa belt, to 3-6 ppm with an average of 4.6 ppm in granitic rocks at Homret Akarem, and up to 7-33 ppm and an average of 16.7 ppm in granitic rocks at Homret Mukpid area ( Table 2).
Beryllium and associated heavy metals' concentration in nearby groundwater. In such deserted areas, groundwater quality has an important role in the agricultural development and human life of the residents. The groundwater samples, collected from the main five shallow groundwater wells (W. Ghazala and W. Sedri) in south Sinai, and (Igla, Um Kabu, and Shazly-Mukpid) in CED, and SED of Egypt, were analyzed for concentrations of Be and associated major ions and heavy metals and reported in Table 3. To assess the groundwater quality parameters, the environmental risk of Be and associated heavy metals, and their potential adverse impacts on the environment and human health. The physicochemical parameters (e.g., pH, TDS, and EC) were measured in the investigated groundwater and reported in Table 3. The analyzed groundwater samples indicated slightly acidic to alkaline groundwaters (pH: 6.38-7.51; average: 6.85), medium to high salinity (TDS: 788-5350; average: 3851 mg/L), and medium (Sinai) to highly flowing groundwater in CED and SED; EC: 1.6-10.87; average: 5.81 mS/cm) ( Table 3). This groundwater locates in a highly fractured basement aquifer at CED and SED, which is related to the brittle deformation associated with the Najd Fault System 51 . The studied groundwater in south Sinai, CED, and SED is more acidic (pH: 6.38-7.51) than the more alkaline groundwater (pH: 7.01-8.09) in Jordan 52 . Similarly, the flow of groundwater (EC: 1.607-10.87 mS/cm) in this study is much higher than (EC: 0.3-1.199 mS/cm) of Jordanian groundwater 38 . Additionally, high concentrations of major soluble ions were detected in the investigated groundwater (Table 3), and their average levels (mg/L) followed the decreasing order: Cl − (5400) > Na + (836.12) > Mg 2+ (300.62) > Ca 2+ (199.57) > K + (22.7) > Si 4+ (11.6) (Table 3). Overall, find- Table 2. Summary statistics of beryllium concentrations (ppm) in the investigated beryl-bearing bedrocks in south Sinai, CED, and SED of Egypt.

Occurrences
Beryl-bearing rocks www.nature.com/scientificreports/ ings revealed that the sampled groundwater from CED and SED contained higher values of physicochemical parameters (e.g., TDS and EC) and major ions than Sinai groundwater ( Table 3). The concentrations of the heavy metals (Be, B, Ni, V, Fe, and Al) were analyzed in the groundwater samples and reported in Table 3. Be is potentially a highly toxic element that may be mobilized especially under acidic conditions in natural waters 23 . Seepage or percolation of Be-contaminated groundwater may result in the accumulation of Be in soil and affecting the soil quality 22 . Few studies worldwide investigated Be concentrations in groundwater nearby beryl-rock mineralization. In Jordan, Be level in groundwater was 0.0006 mg/L 52 . Be level (0.00022 mg/L) was detected in neutral groundwater derived from granite rocks in southern Scotland 23 . In Germany, groundwater contained low Be levels with an average of 0.000008 mg/L 53 . A higher Be level (0.035 mg/L) was detected in the groundwater of Mexico 54,55 , while in the groundwater of Middle Russia, Be concentration was 0.009 mg/L 56 . The Ontario Ministry of Environment has set an environmental quality standard and maximum concentration level (MCL) of 0.004 mg/L for Be in groundwater [56][57][58] , and reported that higher Be levels could be toxic 22 .
In this study, Be concentrations in the investigated groundwater samples from south Sinai, CED, and SED of Egypt ranged from 0.00016 to 0.00044 mg/L and with an average of 0.00032 mg/L (Table 3), which is below the Be (0.004 mg/L) MCL 57,58 . One of the main sources of Be compounds in groundwater is the weathering of bedrocks (e.g., Na-feldspar and biotite granites) and soils containing Be 22,53,59 . Moreover, the highest Be concentrations occur in shallow and deep groundwaters in non-carbonate rocks 23,59 . Be levels in the investigated groundwater in this study were compared to those previously reported in groundwater around the world and followed the decreasing order: Mexico > Middle Russia > Jordan > Egypt (this study) > Scotland, UK > Germany. Most of these samples were restricted to acid groundwaters (pH < 7) and all measurable concentrations were found in noncarbonate rocks. Therefore, Be occurrence depends strongly on geology 22,52 .
The average concentrations of heavy metals associated with Be (mg/L) in the investigated groundwater, followed the decreasing order: B (0.627) > V (0.514) > Fe (0.463) > Ni (0.227) > Al (0.092) > Be (0.00032) ( Table 3). Spatially, high levels of Be, and Ni were detected in the investigated groundwater from W. Ghzala, southeastern Sinai (Table 3 and Fig. 8c), while high levels of Fe and Al were recorded in groundwater of W. Sedri, southwestern Sinai (Table 3 and Fig. 8b). Additionally, high level of B was detected in groundwater of Igla-Asly well, in CED (Table 3 and Fig. 10a), and those of V was in groundwater of Um Kabu well, SED (Table 3 and Fig. 10b).
The bivariate plots show the significant relationships between beryllium, pH, major ions, and associated heavy metals in the investigated groundwater of south Sinai, CED, and SED of Egypt (Fig. 11). Spatially, Be concentrations in groundwater (mg/L) were plotted versus those in beryl-bearing bedrocks (ppm) in the study area, showing that W. Ghazala, southeastern Sinai had the highest Be levels in both bedrock and groundwater, and Homret Mukpid area, SED (where Shazly well is located) showed moderate Be levels in bedrock and groundwater, while W. Sedri, southwestern Sinai, and Zabara-Um Addebaa belt (where Um Kabu well is located), SED (Fig. 10b) exhibited low Be levels in bedrocks and in groundwater as well (Fig. 11a). Noteworthy, Be concentration is unlikely to exceed 0.0002 mg/L in most acidic groundwater 23 . It is reported that zeolites could be used in normal filter beds for Be removal up to 0.0016 mg/L in groundwater 53 .
Some heavy metals associated with Be in groundwater showed significant relationships with pH and major ions. Al was negatively correlated with pH (R 2 = 0.35; p < 0.05) (Fig. 11e) indicating that both Be and Al have similar geochemical controls 22,52 . Ni was negatively correlated with Si 4+ (R 2 = 0.89; p < 0.05) (Fig. 11f) and Ca 2+ (R 2 = 0.5; p < 0.05) (Fig. 11g). In contrast, V showed a highly significant and positive correlation with Mg 2+ (R 2 = 0.518; p < 0.05) (Fig. 11h). Overall, Fig. 11 indicates a general decrease in Be and associated heavy metals with increasing pH of groundwater, which is the usual trend with cationic metals in groundwater of Jordan 52 .
Be behavior with associated heavy metals (e.g., Al) and major ions (e.g., Mg 2+ ) along with pH interval, has environmental and human health importance due to the potential intake of Be by living organisms in water 23 . Accordingly, concentrations of heavy metals associated with Be in the investigated groundwater were compared to their corresponding MCLs 57 to assess their potential adverse impacts on the environment and human health. As a result, all B levels (0.166-1.282 mg/L) in groundwater are below (1.4 mg/L) the MCL 57 .
Overall, most levels of Be, B, Ni, Fe, Al, and V in groundwater in the investigated groundwater of south Sinai, CED, and SED are below their corresponding MCLs 53 (Table 3; Fig. 11).
The mean values of eTh/eU of W. Ghazala (4.8), which is higher than the recommended Clark value  Table 1). Among the estimated mean 238 U and 232 Th, and 226 Ra activity concentrations of the studied beryl-bearing rocks, Homret Mukpid (79, 87.15, 60.26 Bq kg −1 ) and Homret Akarem (111.6, 51.17, 85.1 Bq kg −1 ) contain the highest values, which are higher than the safety world levels 40 . This is may be attributed to their highly fractionated granitic rocks that host uranium and thorium reservoir minerals such as zircon, allanite, and monazite 16,19,21 . The 238 U and 232 Th activity concentrations of the examined Homret Mukpid and Homret Akarem are also higher than those of Homrit Waggat Area 16 .
On the other hand, the mean 232 Th/ 238 U values of beryl-bearing rocks in W. Ghazala, W. Sedri, Homret Mukpid, Igla, Zabara-Um Addebaa belt, Homret Akarem areas are (1.66, 1.46, 1.18, 1.14, 0.33, and 0.43, respectively, which are less than the recommended mean value 20,51 . Skewness and kurtosis are the main descriptive statistics that were performed for the studied emerald and beryl-bearing rocks in Egypt. The skewness factor is applied to the examined samples to infer asymmetric distribution. Positive and negative values of activity concentration in different areas reflect symmetric and flatness distributions, respectively. Furthermore, negative, and positive kurtosis coefficients suggest flat and preakness distribution, respectively. Figure 11. Bivariate plots show the relationship between concentrations of beryllium and associated major ions and heavy metals (mg/L) in this study. Be in groundwater versus Be in nearby rock occurrences (ppm) (a), B (b), pH (c) and Cl -(d); As versus K + (e); Al versus pH (f); Ni versus Si 4+ (g), and Ca 2+ (h); and V versus Mg 2+ (i).  46), and Homret Akarem (0.69) areas are lower than unity (Fig. 12). This reflects that there is no significant risk associated with these rocks 16 .
The effective dose (D organs ) to human organs per year is computed in Table 4. The radiation amassed in human organs for a person can be detected by D organs . It is noticeable that the outdoor D organs data are lower than those of indoor D organs and both are less than unity (recommended levels) 62 . In addition, the indoor and outdoor (D organs ) for liver receive the lowest dose relative to otherhuman organs. Controversy, indoor and outdoor for testes receive the highest dose 62 . Furthermore, indoor, and outdoor (D organs ) of Homret Mukpid contain the highest values relative to other areas.

Conclusions
Beryllium concentrations in beryl-bearing bedrocks in south Sinai (Wadi Ghazala and Wadi Sedri), CED, and SED of Egypt (Zabara-Um Addebaa belt, Homret Akarem, Homret Mukpid) were investigated in this study. The environmental risk levels of Be and associated major ions and heavy metals in shallow groundwater nearby to beryl-bearing mineralization were also evaluated. Results showed that Be concentrations ranged from 1 to 374 ppm in beryl-bearing bedrocks, while in nearby groundwater, Be has a range of 0.0001-0.00044 mg/L with an average of 0.00032 mg/L, which is within the permissible level and below (0.004 mg/L) the U.S. EPA maximum contaminant level (MCL). Considerable levels of heavy metals; Be, Ni, Fe, V, and Al were detected in the groundwater of south Sinai, while the groundwater from CED and SED of Egypt contained abundant levels of B, V, and major ions. The average levels (mg/L) of major ions in groundwater followed the order: Cl − (5400) > Na + (836.12) > Mg 2+ (300.62) > Ca 2+ (199.57) > K + (22.7) > Si 4+ (11.6). While the average of heavy metals in groundwater followed the order: B (0.627) > V (0.514) > Fe (0.463) > Ni (0.227) > Al (0.092) > Be (0.00032). The radiological risk of natural radionuclides distributed in beryl-bearing bedrocks was investigated and evaluated in this study. Among the investigated areas, Zabara-Um Addebaa belt has the lowest mean values of eU (1.33 ppm) D organs out (mSv y −1 ) D organs in (mSv y −1 )  www.nature.com/scientificreports/ and eTh (2.1 ppm). On contrary, Homret Akarem and Homret Mukpid contain the highest eU (9 ppm) and eTh (21.57 ppm), respectively. Radiological risk parameters (outdoor and indoor annual effective dose, radium equivalent activity, internal and external indices, index of excess cancer, and effective dose to human organs) were estimated for the studied emerald and beryl-bearing rocks to infer the radiation effect on human organs. The study findings reveal that there are no significant or adverse impacts associated with the investigated berylbearing rocks and nearby groundwater of south Sinai, CED and SED of Egypt.